YS-RCS-BS-06

WALL DESIGN

Problem

Design grade 45 braced reinforced concrete wall in 7.65m length, 3.9m height and 225mm thick. The wall is subjected the following initial design forces:

Axial 15500kN, bending moment about major axis at the top 13000kNm, bending moment about major axis at the bottom 6400kNm, bending moment about minor axis at the top 50kNm, bending moment about minor axis at the bottom -20kNm.

Let the cover to reinforcement as 25mm.

Solution

1. Arrange the reinforcement in wall section.
2. Determine whether the provided reinforcement fulfills the limiting values as per Table 3.25, cl.3.12.6.3, cl.3.12.7.4 & cl.3.12.7.5, BS8110-1:1997.
3. Determine the top and bottom end conditions about both major and minor axes, based on Table 3.19 & Table 3.20, BS8110-1:1997.
4. Calculate the effective height of wall by referring to cl.3.8.1.6.1, BS8110-1:1997.
5. Calculate the wall slenderness ratio based on cl.3.8.1.7 & cl.3.8.1.8, BS8110-1:1997.
6. Determine the type of wall in accordance with cl.3.8.1.3, BS8110-1:1997.
7. Calculate the minimum eccentricity based on cl.3.8.2.4, BS8110-1:1997.
8. Calculate the minimum design moment due to eccentricity based on cl.3.8.3.2, BS8110-1:1997.
9. Determine initial design moment by referring to cl.3.8.3.2, BS8110-1:1997.
10. For slender wall, carry out calculation as per step 11 to 16. For stocky wall, proceed to step 17.
11. Calculate the ultimate capacity of wall when subjected to only axial load, as per cl.3.8.3.1, BS8110-1:1997.
12. Calculate the axial capacity of the wall under balanced section condition, as per cl.3.8.1.1, BS8110-1:1997.
13. Determine the wall deflection reduction factor in accordance with cl.3.8.3.1, BS8110-1:1997.
14. Determine βa based on cl.3.8.3.1, BS8110-1:1997.
15. Determine the deflection of slender wall by referring to cl.3.8.3.1, BS8110-1:1997.
16. Calculate the additional moment due to slender wall deflection, as stated in cl.3.8.3.1 & cl.3.9.3.7.3, BS8110-1:1997.
17. Determine the design moment about the target axis, referring to Figure 3.20, BS8110-1:1997.
18. Determine h' and b', as defined in Figure 3.22, BS8110-1:1997.
19. Calculate the ratio of Mx/h' and My/b'.
20. Calculate N/bhfcu.
21. Determine the value of β as per Table 3.22, BS8110-1:1997.
22. For biaxially bent wall, determine design equivalent uniaxial bending moment by referring to cl.3.8.4.5, BS8110-1:1997.
23. Develop axial and bending interaction curve about both axes for wall, based on cl.3.4.4.1, BS8110-1:1997 and Appendix A, BS8110-3:1985. Click here for detailed steps.
24. Plot the design axial and bending moment on interaction curve and evaluate the wall design. The design is inadequate if the point lies outside the envelope of curve.